Chronic increases in wall stress play a pivotal role in the initiation and progression of cardiomyopathy and associated heart failure. Experimental and human studies point to a critical role of cytoskeletal defects, with a clustering of mutations in genes encoding components of the Z disc and their interaction with titin and titin-associated proteins. Human mutations in titin, telethonin, and muscle LIM domain proteins (MLP, Cypher), have now been clearly implicated in the onset of human cardiomyopathy. In addition, Z disc proteins and the titin complex have recently been identified as an essential part of the cardiomyocyte biomechanical stretch sensor, suggesting that defects in cytoskeletal-dependent stress signaling pathways may be linked to the initiation and progression of human DCM. It will become critical to mechanistically link the complex Z disc and titin associated proteins that contribute to human heart failure. We have uncovered a number of new cardiac cytoskeletal-associated proteins that physically interact with titin, actin, and other components of the cardiac-stretch mediated responses. This proposal will capitalize on these novel cytoskeletal associated proteins, new mouse knockouts of these genes, new in vitro and in vivo assay systems that will allow a precise evaluation of the upstream and downstream signaling pathways that link them to key endpoints, and state-of-the-art transcriptional profiling and bioinformatics to identify downstream target genes. A direct evaluation of their mechanistic role in exacting a cause-effect relationship with stretch mediated responses will be evaluated by capitalizing on new assay systems in cultured cells, intact papillary muscle, and in the in situ heart to evaluate the role of these in stretch mediated responses. Accordingly, the Specific Aims of this proposal are: 1) To identify the mechanistic links between a gp130 dependent, biomechanical stress-inducible cytoskeletal associated protein (SprMA) and pathways for cardiomyocyte hypertrophy and survival; 2) To delineate the role of a titin-associated, stress inducible protein (CARP) in the transduction of downstream signals for cardiac hypertrophy during biomechanical stress; and 3) To define the role of myopalladin, a muscle restricted component of the CARP-titin complex, in biomechanical stress induced pathways for cardiac hypertrophy and cardiomyopathy. [unreadable] [unreadable] [unreadable] [unreadable]